Former White House chief strategist Steve Bannon slammed Republican Senator Bob Corker for his public sledging of the Trump White House as "an adult daycare center," declaring him a "real piece of work" in a speech at a conservative summit on Saturday.

"Bob Corker has trashed the Commander-in-chief of our Armed Forces, while we have young men and women in harm's way," said Bannon at the Values Voter summit, a highly conservative political convention in Washington, DC.

Bannon, who returned to his role as executive chairman at Breitbart News after leaving the White House in August, declared it a "season of war" in the GOP.

He argued repeatedly that it was particularly bad for someone to insult the president while the country has troops fighting in wars.

Trump has previously said of McCain, who spent more than five years as a prisoner of war in Vietnam: "He’s not a war hero...I like people that weren’t captured."

Jake Tapper from CNN noted that it was definitely not the first time a US president had been mocked by a senator during wartime, noting that previous stories about senators mocking President Barack Obama ran on Bannon's own Breitbart.

Bannon's speech on Saturday railed against the GOP establishment, calling it a "civil war inside the Republican party," and slammed those who didn't defend the president from Corker's comments, naming John Barrosso of Wyoming, Dean Heller of Nevada, and Deb Fischer of Nebraska.

"Have I seen [John] Barrosso come to a stick and condemn that?" he asked.

"Let me give a warning to you: no one can run and hide on this one. The days of taking a few nice conservative votes and hiding is over," declared Bannon.